US 2006/0229515 A1 discloses an optical method and apparatus utilized to evaluate the presence of tissue modification, in particular, to evaluate tissue ablation using light scattering spectroscopy realized via optical fibers. The evaluation of tissue ablation by using light scattering spectroscopy is relatively inaccurate, because of the small penetration depth of the light into the tissue and because of significant variations in tissue structure and tissue perfusion, which adversely affect the interpretation of light scattering spectra.